The invention relates to a method of producing a relatively soft, essentially planar, though three-dimensional product and to a corresponding product itself. Such products as largely planar products are usually increased in terms of their volume by means of an embossing process. This increase in volume (bulking) may affect appearance on the one hand, and technical properties on the other. If a tissue or a similar paper product for example is provided with an embossment, the properties of touch and feel can thereby be improved in addition to an enhanced appearance. As well as these properties of touch, the product""s absorption properties may also be improved by the starting product""s conversion as a result of embossing. As far as the method and product according to the invention are concerned, a wide variety of materials is relevant, particularly e.g. with regard to paper: tissue (creped or uncreped, wet-laid, single-layered or multilayered), absorbent cotton; with regard to textiles: all soft textiles, woven fabrics, so-called xe2x80x9cnon-wovensxe2x80x9d (e.g. dry-laid), textile laminates; with regard to synthetics: all soft plastics as a foil or fiber composite; with regard to leather: all soft leathers; with regard to metal: thin metal foils, particularly aluminum foils.
As far as embossing is concerned, a wide variety of embossing techniques is relevant, as are already well-known to the skilled person.
In terms of the known techniques, the invention is based on the problem (object) of creating a product of the aforementioned type which has much improved visual and/or tactile properties by use of simple means.
This problem is solved by a method of producing a relatively soft, essentially planar, though three-dimensional product including the production steps of:
a) converting a relatively soft, essentially flat planar initial product by embossing a three-dimensional pattern that generates a primary bulk with respect to the initial product; and
b) stretching this intermediate product achieved by embossing of the initial product essentially in the direction of its largely planar extension for generating a superimposed, secondary bulk with respect to the intermediate product.
It is a surprise that at least in terms of appearance and tactile properties, an embossed intermediate product can consequently be improved in a particularly simple manner in terms of a secondary bulk when the embossed intermediate product undergoes a stretching process.
This secondary bulk particularly has the effect as a superimposition of that bulk which was brought about by embossing when the intermediate product""s embossing pattern is formed from a plurality of hinged parallelograms crosslinked together and when stretching takes place to optimum effect for example in a direction which runs diagonally through the parallelograms and particularly through diagonally opposite hinge points, which do not of course represent genuine hinge points in the mechanical sense but are arrived at from the embossing process to the extent that lines of compressed material intersect and limit the parallelograms which when crosslinked subsequently act in a manner similar to a pantograph when the stretching forces are applied.
Bulking is defined by the largely planar initial product""s raised (bulged) portions that are produced by embossing, with the result that bulking primarily takes place in the direction perpendicular to the large surface of the initial product.
The phrase xe2x80x9crelatively softxe2x80x9d implies the necessity of actually being able to perform an embossing process. The phrase nevertheless also implies the product""s deformability to the extent that a lasting deformation can be achieved by the stretching process just as much as it can be achieved by the embossing process. The product is also intended to have a certain and optionally a particular flexibility and softness in its final state, depending on the actual application and depending on whether emphasis is placed on the appearance or on tactile properties.
The problem is also solved by a relatively soft, largely planar, though three-dimensional product that has a three-dimensional embossing pattern and a secondary bulk superimposed on this embossing pattern as an inherent primary bulk. The secondary bulk may be convex and it may be disposed on the convex side of the embossing pattern which forms the primary bulk. The secondary bulk in this sense may be concave.
The embossing pattern need not, but may, be symmetrical.
The secondary bulk can be achieved in a particularly beneficial manner if within the embossing pattern, the individual embossed shapesxe2x80x94as a horizontal projectionxe2x80x94have a form which is located between the shape of a circle and that of a square or rectangle. A clear deviation from the circular form is nevertheless to be present. For example, the embossing pattern on the whole forms a rhombic pattern.
Lines that are essentially embossed on a plane are expediently formed in the embossing pattern between the individual shapes; these lines are connected together and four thereof respectively form a xe2x80x9chinged parallelogramxe2x80x9d. Many such hinged parallelograms are crosslinked together, as has already been mentioned in conjunction with the method. These lines intersect one another, whereby the points of intersection form hinge points in a manner resembling a pantograph when the aforementioned stretching forces are applied in the correct manner. The lines may be linear, but do not have to be so, between these intersections (hinge points). They may adopt a curved course such as in a so-called oriental or Venetian pattern. What is essential is the behavior as a pantograph when corresponding stretching forces are applied.
The relatively soft, largely planar, though three-dimensional product is particularly obtainable by means of a planar three-dimensional intermediate product provided with an embossing pattern that forms a primary bulk and which is produced by using an embossing tool; as a result of stretching essentially in the direction of its largely planar extension, this intermediate product is lent a lasting secondary bulk that is superimposed on the primary bulk. In other words, the embossing tool based on its design substantially affects the superimposed lasting secondary bulk brought about by stretching.
The use of a so-called xe2x80x9cfemalexe2x80x9d embossing tool that has recesses into which the material of the planar initial product is pressed for the lasting primary bulk is particularly expedient. In this regard, the embossing tool does in fact comprise webs that are connected with one another between the recesses and which together with the recesses lend the intermediate product an embossing pattern in that convex (raised) portions corresponding to the recesses are limited by lines of compressed and hence strengthened material, these lines being embossed by the webs. As a result of xe2x80x9cfemalexe2x80x9d embossing, these lines form in a particularly beneficial manner hinged parallelograms connected together in a network-like way such that this network acts as a pantograph when opposite stretching forces are applied in the direction of the large planar extension and essentially in the diagonal direction of the intermediate product""s hinged parallelograms. Correspondingly, the hinged parallelogram should be oriented with respect to the machine direction if the stretching is made in machine direction.
Secondary bulking can be achieved particularly effectively when within the embossing tool, the side walls of the recesses extend on all sides at a specific acute angle, starting from the tool surface. This angle should preferably be not less than about 40xc2x0 and particularly not less than about 60xc2x0. In a particularly advantageous manner, this angle amounts to 65xc2x0.
The number of individual shapes per square centimeter also positively influences the formation of the secondary bulk. In this way, this number of individual shapes per square centimeter may be 0.5 to 6 and particularly 1 to 2.5.
The dimension of the embossing tool""s recesses likewise affects the formation of the lasting secondary bulk as a result of stretching. In this way, the ratio of the depth of the recesses to the width may be 0.1 to 0.5 and particularly 0.2 to 0.3.
The recesses within the embossing tool may comprise graduated side walls such that starting from the tool surface, a plurality of wall portions is juxtaposed into the depth of the recesses and the acute angles formed by the wall portions relative to the tool surface decrease in size from wall portion to wall portion.
The webs between the embossing tool""s recesses may preferably have a width of 0.5 mm to 3 mm and particularly of 1.2 mm to 2.2 mm. A profile may also be provided within these webs and a row of recesses formed along these webs may particularly be provided therein. As a result, raised (bulged or convex) portions are formed as additional bulks within the product""s embossed lines.